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So I got a little carried away applying shellac for the first time and didn't wait long enough between coats. The result was a gloopy looking, cloudy surface. On the paduak the coat actually looks like runny peanut butter in some places ...

Should I scrape off the excess and apply one final light coat, or sand it?

edit:

Apparently the denatured alcohol can dissolve foam brushes. I am guessing this is where the nasty looking color is coming from. I guess I should scrape it down to the wood and start fresh with a cut up t-shirt ...

  • Yeah you've got to be careful of solvents eating foam brushes :-) – Graphus Mar 23 '17 at 8:22
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I would sand it and begin again. For brushing, I see folks recommending fine nylon brushes but I prefer a fine China bristle brush when I'm not spraying. Here's some recommendations I make with shellac.

Most commercially prepared shellac is typically a 3 lb. cut and should be diluted before brushing. This will allow the first coat a bit more penetration. But more importantly, it helps you work faster on subsequent coats. Like lacquer, shellac dissolves the underlying layers as you apply additional coats. If you "work" it too much you will drag underlying material and create uneveness.

Be absolutely sure the shellac is fresh. I usually mix my own from flakes for guitar work but the Zinsser brand is OK for less critical applications. Try to find stock less than 6 months old. They used to date the cans but how use a code. Here's a link to "decode": https://woodworkersedge.wordpress.com/2012/07/15/decode-your-shellac/

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  • I should have mentioned this but I got garnet dewaxed tiger flakes and mixed about at about 2 lbs cut. – jbord39 Mar 23 '17 at 3:43
  • @jbord39. That sounds good for your build coats. You may still want to dilute the first coat, applying as a "wash coat". Be deft and avoid reworking the wet surface. – bpedit Mar 23 '17 at 4:50
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You should at least remove the excess if you've gotten a sort of gloopy/lumpy surface. This can be done quite effectively by a version of "spiriting off" where you wipe with a pad dampened in alcohol. With care you can remove excess shellac without revealing bare wood in spots and along edges.

If you need to get all the way back to bare wood you can wipe it away with paper towels or a cloth soaked in DA at any stage in the drying process from still sticky to fully hardened, or scrape it off or sand it off as you prefer.

With sanding you need to wait until the shellac has hardened sufficiently so that it doesn't gum up the paper (how long is needed is entirely dependent on the temperature and humidity at your location). It's often best to wait the same amount of time if scraping but not absolutely necessary since you can't clog a scraper in the same way!

start fresh with a cut up t-shirt ...

I'm a big fan of wiping on shellac on small items (not so much for larger stuff) so I think you should at least try it once or twice to see how you get on. If you're deft and fast you can get away with just wiping on with some shellac soaked into a pad of cloth or paper, but to work the shellac into the surface and build a more uniform coat you need to adopt a more full-on French polishing technique and lubricate the pad's surface with a drop or two of oil.

Traditionally the oil used was raw linseed oil but actually the type of oil doesn't really matter as it doesn't become a part of the finish, and many today use mineral oil instead. The oil eventually is removed from the surface by wiping/buffing or during spiriting off.


Re. spiriting off, I wish I could point you to a definitive source but actually I've found there are numerous variations, even among pros. Any decent guide to French polishing, including just a chapter in a wider book on finishing, should include a description of one version of it. Given the authority of the writers presenting the variations I have to assume that all of them do the job and minor differences may simply be a matter of personal preference.

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